Field of the Invention
This disclosure relates to an image forming apparatus and, more particularly, relates to an image forming apparatus which combines an image signal with a trace pattern.
Description of the Related Art
In the types of an image forming apparatus, there is a type in which a specific trace pattern is combined with (superimposed on) a signal of an image to be printed for each image forming apparatus. When an image such as a banknote and a security for which copying is prohibited is formed by superimposing a trace pattern on an image signal, it is possible to identify (trace) an image forming apparatus which prints the image.
In relation to a technology for combining an image signal with a trace pattern, JP 2004-289873 A (JP 2004-289873 A) discloses a configuration in which the distinctiveness and the latency of a trace pattern are not reduced even when the concentration of a record image to be formed is changed. More specifically, JP 2004-289873 A discloses a configuration in which a lookup table used for gamma correction by a gamma correction circuit is selected in accordance with the deviation between the concentration of a measured toner patch and a target value and, aside from this, a trace pattern to be added to input image data is selected.
However, there is a problem in that the visibility of a trace pattern is changed according to the usage conditions of an image forming apparatus. In this regard, the technology disclosed in JP 2004-289873 A does not consider it at all. Thus, in the technology, there is a possibility that it is not possible to decode a trace pattern under the condition where, for example, the visibility of the trace pattern is reduced.